Eocene Fossils of the United States. 221 
with the base and sides rather thick and porous, and resembling much 
in texture and the lamellz of the cells the Dendrophylliz. The thick- 
ening of the corallum is described as taking place from within through 
foramina, and upon this character the genus is founded, and to it the 
name alludes—from éJov within, and aazus thick. On an examination 
of specimens of the same species figured by Lonsdale, I see no evi- 
dence of this anomalous mode of secretion; they appear very similar 
in character to some Dendrophyllix, except that they are free and sim- 
ple, and are different in shape, and exterior markings. After an ex- 
amination of numerous coral zoophytes in the living state, I am led to 
doubt the propriety of the grounds upon which the genus is based. 
But one principle as regards the secretion of coral, runs through all 
the species of the Caryophyllia and Astrea tribes, as far as examined 
by the writer, and in all instances they appear to be internal secretions, 
very analogous in mode of formation to the calcareous secretions of 
other animals. 
' The Madrepora tubulata of Lonsdale, in the same memoir, is an 
Oculina. 
The Columnaria sexradiata, is allied to the Astrea calicularis of 
the Mediterranean, for which I have adopted as a generic name, Astro- 
itis, from Boccone. The recent species is characterized by long prom- 
inent polyps when expanded, and has not the terminal mode of bud- 
ding which distinguishes the genera of the Astrea tribe. The subdi- 
vision of polyps which takes place in most Astreas is the result of disk- 
budding ; but in these species the polyps are only united to one an- 
other at base, and the buds are therefore basal or lateral, instead of 
terminal, and make their appearance in the interstices. The exposed 
polyps are prominent, because they secrete lime only in their lower 
or basal portions. | 
The species referred to the Astrea hirto-lamellata of Michelin by 
Lonsdale, is closely allied to the preceding, and either belongs to the 
same genus, or to the group Pleiadia of the writer, which is distin- 
guished from Astroitis by having the cells of the corallum solidly 
coalescent. An allied species before me has the interstitial mode of 
budding of the Astroites, and judging from analogy, the polyps were 
probably prominent, as in that genus. ; 
